1. Field of the Invention
This invention relates generally to roofing and construction technology and, specifically, to new roofing shingles formed from polymeric compositions.
2. Description of the Prior Art
Conventional asphalt shingles are widely used in the construction and roofing industries at the present time. These materials are typically formed of a lower layer of asphalt, an intermediate layer of base made from either fiberglass or felt, an upper layer of asphalt, and a layer of weather resistant granules. The felt is usually impregnated with the asphalt from the upper and lower layers. The voids between the individual fibers of glass in the fiberglass are usually occupied by asphalt from the upper and lower layers, which also coats the fibers. The shingles can be attached to the roof by conventional means, including nails or staples.
In production, conventional asphalt composite shingles are made in a hot asphalt coating process as a continuous sheet of composite material with the width being dictated by the design of the coating equipment. The sheet is fed into a cutting device which cuts individual shingles from the sheet. As mentioned, the exposed, outer surface of the asphalt shingle is generally provided with a covering of granular material embedded within the coating of asphalt. The granular material generally protects the underlying asphalt coating from damage due to exposure to the light, particularly ultraviolet light. The granules reflect light and protect the asphalt from deterioration in the sun. In addition, such granular material improves fire resistance and weathering characteristics. Further, colors or mixtures of colors of granular material may be selected for aesthetics.
Generally, the mineral materials, particles or granules are embedded within the coating of asphalt under pressure and are retained therein by adherence to the asphalt. Granule loss can occur due to many factors, such as aging or physical abrasion, as when a person walks on the roof. Loss of the granules reduces the life of the traditional composition shingle roof. In addition, the aesthetics of the roofing system may be compromised if granules are lost. Further, reduction of fire retardancy, and hence safety conditions of the roof may be compromised.
In addition to granule loss and deterioration, the prior art composition shingles were relatively heavy, as compared to, for example, synthetic materials of the same square area and thickness.
A need exists therefore for an improved roofing shingle which overcomes the prior art problems of deterioration, granule loss and loss of fire retardancy.
A need exists for such a roofing shingle made from a polymeric composition, rather than from asphalt based materials, which eliminates the need for incorporation of granules into the formulation.
A need also exists for such an improved shingle made from a polymeric composition which is lighter in weight per roofing square than the prior art asphalt composition roof shingles.
A need also exists for such an improved roofing shingle which exhibits adequate fire retardancy without the necessity of incorporating additional fire retardant ingredients, coatings or agents into the polymeric formulation.
The present invention comprises a shingle composition for the roof of a structure. The improved composition comprises:
(a) a rubber component present in the range from about 5-95% by weight, based on the total weight of the composition;
(b) a polyolefin component present in the range from about 5-70% by weight, based on the total weight of the composition;and
wherein the shingle composition is further characterized as having a weight of less than 150 pounds per roofing square at xe2x85x9 inch thickness and which meets the flame retardancy requirements of FMVSS-302 at thicknesses of xe2x85x9 inch and higher without the addition of separate flame retardant components.
Preferably, the shingle composition comprises:
(a) an styrene-butadiene copolymer rubber component present in the range from about 10-95% by weight, based on the total weight of the composition;
(b) an ethylene vinyl acetate copolymer component present in the range from about 5-50% by weight, based on the total weight of the composition.
A particularly preferred shingle composition is further characterized as having a Shore A hardness as measured by ASTM D 2240 of approximately 70, a density as measured by ASTM D 3575 of approximately 22.5 pounds per foot and a tensile strength as measured by ASTM D 412 of approximately 270 psi. The preferred shingle composition has a minimum elongation as measured by ASTM D 412 of approximately 200% and a resilience as measured by ASTM D 2632 of approximately 34%.
Additional objects, features and advantages will be apparent in the written description which follows.